The present invention relates to a portable chamfering device for chamfering the end of a metal tube, and more particularly, it relates to a device comprising an abrasive wheel and a portable pneumatic motor coupled to the wheel and capable of rotating the wheel at greater than 10,000 r.p.m., which device is especially useful to chamfer steel tubes which are fixed in place and are in confined spaces so as to prepare these tubes for welding.
In the construction, repair and maintenance of large equipment which utilize thick-walled steel tubes, such as boilers, it is often necessary to replace or install a section of tubing. This is usually done by welding the ends of the section to two other parts of the tubing which is fixed in place. In order to form a proper weld connection, the ends of the tubes to be connected must be chamfered.
This chamfering must be done accurately and at the ASTM recommended angle of 37.5.degree. so that the weld is successfully accomplished. It also must be done quickly due to high wages paid to the machinist doing the work and a welder who is usually standing by to do the welding. Moreover, this chamfering usually must be done in a confined space in the region of the boiler where the tubes are fixedly located.
In the prior art, various devices have been utilized to provide a chamfer at the end of metal tubes for preparation for welding; however, they all have various drawbacks which make them unsuitable to do the activity set forth above. Thus, some are very bulky and therefore can not be maneuvered into confined spaces. Other prior art devices utilize disc-shaped grinding stones; however, these take an extremely long time to perform the chamfering and they are not very accurate. Other devices utilize very heavy stone grinding wheels; however, because of their heaviness, they cannot be held by a machinist for long periods of time and accordingly, the chamfering takes significantly more time since the machinist must rest periodically. In addition, these heavy stone grinding wheels cannot be rotated at very high speeds and therefore chamfering with them takes an exceedingly long time. Moreover, various prior art devices utilize metal blades; however, they frequently break at high speeds and require significant amounts of time in replacing these broken blades.